24 Bulletin American Museum of Natural History. [Vol. XXIII ^ 



that in all of them the enlargement of the gaster is due to Mermis parasites.' 

 Ill addition to the above mentioned forms he also describes mermithergates- 

 in Pachycondyla juscoatra from Bolivia, and in the well-known South Amer- 

 ican Paraponera clavata. 



Both Emery (/. c, p. 591) and Wasmann^ object to my applying the 

 name macroergates to the Pheidole workers parasitized by Mermis. The 

 latter author, who coined this term, applies it to "abnormally large workers 

 with normal development of the gaster," and in another place,^ to "individ- 

 uals which approach the females abnormally in the size of the body, but in 

 other respects (even in the development of the gaster) are normal workers. "^ 

 I am quite willing to be corrected, but it should be pointed out that the gaster 

 in the adult pupae of the mermithergates of Ph. commutata, and probably 

 also of the other species, is normal in its proportions, the enlargement being- 

 confined to the imaginal instar. It is merely a mechanical dilatation such 

 as is seen in the repletes, or plerergates of the honey ants (Myrmecocystus) 

 and in Wasmann's "gyna?coid workers," which are merely workers whose 

 ovaries contain mature eggs. Although the dilatation in these different 

 cases is due to the difference in the contents of the gaster (liquid food, ovaries 

 or parasites) the morphological results are the same. Even had the objection 

 to the use of the term macroergates been based on the presence of the ocelli,, 

 it would not have been greatly strengthened, for these may be absent in 

 specimens to which the term would seem to be applicable. In my opinion 

 it may be permissible to distinguish three classes of macroergates, namely: 

 macroergates proper (as defined by Wasmann), mermithergates, and 

 plerergates. 



Emery adds to his observations an interesting hypothesis. He says (pp. 

 601-603): "I believe that the singular microcephaly of the worker ants 

 infested with Mermis may be attributed to a general law of growth of the 

 ant-body and perhaps also of the insect body in general. 



"We must assume with Wheeler that the parasitic nematode enters the 

 ant larva and has already attained a considerable size before its metamor- 

 phosis. As long as the larva retains its cylindrical, spindle, or clavate shape, 

 the worm, no matter whether it is injurious to the growth and development 

 of the larva or not, will have only a slight influence on the external form. 

 But as soon as the constriction appears at the anterior end of the abdomen 

 during the preparation for the pupal stage, and the whole worm is relegated 

 to the latter region, the defective nutrition of the larva makes itself felt in 



1 Zur Kenntniss des Polymorphismus der Ameisen. Zool. Jahrb. Suppl., VII, 1904, pp. 

 587-610, 9 figs. 



2 Ameisen arbeiterinnen als Ersatzkoniginnen. Mittheil. d. schweiz. entomol. Ges., XI, 2, 

 1904, p. 67. 



3 Die ergatagynen Formen bei den Ameisen und ihre Erklarung. Biol. Centralbl., V, 1895, 

 p. 606. 



